Apparatus for acquiring human finger manipulation data

ABSTRACT

An apparatus for acquiring human finger manipulation data includes at least one finger motion detector consisting of a force sensor to be fitted on a human fingertip, at least three links and at least four angle detectors; and a base supporting the finger motion detector. The base can be attached to an external mount or a human hand. The force sensor is connected to the base through a link mechanism constituted by the links, and the angle detectors are attached at pivots between the links and optionally at a pivot between the link mechanism and the base. Three-dimensional motion of the finger is determined by measuring data of the angle detectors of the link mechanism, and fingertip contact force is measured by the force sensor. Up to five finger motion detectors, one for the thumb and each finger, can be supported on the base.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] This invention relates to an apparatus for acquiring human fingermanipulation data useful for analyzing manipulative motions of the humanhand in order to acquire data regarding motion of the human fingers andforce acting on the fingertips for application of the data to control ofa robot hand. (Except as otherwise obvious from the context, the term“finger” used in this specification includes the thumb).

[0003] 2. Description of the Prior Art

[0004] Conventional devices developed for acquiring data regarding humanfinger motion include one type consisting of a glove having bendingsensors whose resistance value changes with finger joint bendingattached by sewing at the back of the finger joints (e.g., Super GloveJr. marketed by Nissho Electronics Co. and Cyber Glove marketed byVirtual Technologies, Inc.) and another type that uses a parallel-linkgoniometer straddling the finger joints (e.g., Dextrous Hand Mastermarketed by EXOS).

[0005] For detecting distribution of pressures acting on the fingers andpalm of the human hand, there has been developed a glove-like deviceworn on the fingers that has a distribution-type tactile sensorutilizing a pressure-sensitive conductive rubber or conductive ink sheetmaterial sewn on the glove (e.g., Glove Scan System marketed by NittaCo.).

[0006] Sensors developed for acquiring data regarding forces along sixaxes include types designed for mounting on the wrist of a robot (e.g.,six-axis force sensor IFS series market by Nitta Co.) and types designedfor mounting on a fingertip of a robot hand (e.g., NANO sensors marketedby BL Autotech, LTD.).

[0007] Analysis of the manipulative actions of the human hand based onacquired human hand grasp/manipulation data provides information thatcan be used to develop a robot hand grasping and manipulation algorithmthat takes advantage of human knowledge and experience. Exploitation ofhuman knowledge and experience opens the way to development of analgorithm for grasping and manipulating paper, cloth, cable and otherflexible materials, which has so far been difficult to accomplish.

[0008] To achieve such grasping and manipulation it is essential tomaintain dynamic balance and dynamic stability in the graspingoperation. Since human finger motion data alone is therefore notsufficient, the contact forces acting on the fingertips must also bemeasured.

[0009] Humans manipulate objects chiefly with the fingertips. Inacquiring human finger motion data, therefore, the importance ofacquiring fingertip motion data far outweighs that of acquiring dataregarding the motion of the individual joints.

[0010] Devices developed up to now for acquiring data regarding humanfinger motion include one that consists of an ordinary thin glove havingbending sensors whose resistance value changes with finger joint bendingattached by sewing at the back of the finger joints (e.g., Super GloveJr. marketed by Nissho Electronics Co. and Cyber Glove marketed byVirtual Technologies, Inc.). When the wearer bends a finger, the devicedetects the finger joint angle from change in the resistance of thebending sensor.

[0011] A joint angle data detector has been developed which uses aparallel-link goniometer that straddles the finger joints with two setsof parallel links whose one side lies perpendicular to the finger linksand whose jointed portions are equipped with angle detectors (DextrousHand Master marketed by EXOS).

[0012] These devices measure the individual joint angles of the humanfinger. In order to determine the motion of the fingertip, therefore, acomplex calibration is required for calculating the effect length of thefinger links.

[0013] As a device for detecting human finger tactile force, there hasbeen developed a sensor glove having a distribution-type tactile sensorutilizing a pressure-sensitive conductive rubber or conductive ink sheetmaterial sewn on the glove (Shimojo et al., “Development of Sensor GloveMKIII for measuring grasping pressure distribution,” The 14^(th) ScienceLecture Meeting of the Robotics Society of Japan, 1996. Also, Glove ScanSystem marketed by Nitta Co.).

[0014] This sensor glove can detect distribution of pressures appliedonto the fingers and palm. However, the detected force components areonly those in the direction perpendicular to the surface of the sensor.When grasping/manipulating an object, a human being is known to utilizefrictional force (tangential to the sensor surface) and moment at thefingertip surface. The sensor glove is therefore inadequate because itcannot detect frictional force tangential to the sensor surface ormoment at the sensor surface.

[0015] When human hand grasping data are used directly for robot handcontrol, the data is preferably acquired using the same type of sensoras used by the robot hand. In this regard, it has been reported that asthe sensor mounted on the fingertip of the robot hand it is important touse a six-axis force sensor (Nagata et al., “Development of aFingertip-type 6D Force Sensor and Error Evaluation of Contact PointSensing,” Journal of the Robotics Society of Japan, Vol. 14, No. 8,1996).

[0016] In view of this finding, the sensor used to detect contact forceacting on the human finger should preferably be a six-axis force sensorthat can be worn on the finger and is able to detect force and moment inthree orthogonal directions.

[0017] Although six-axis force sensors for robots have been developed,even the smallest, the NANO sensors produced by BL Autotech, Ltd.,measure 18 mm in diameter and 32.8 mm in length. Existing six-axis forcesensors are therefore too large to be worn on the human fingertip.

[0018] In light of the foregoing circumstances, the inventor earlierdeveloped a force sensor worn on the finger comprising a fingerstall forfinger insertion, an elastic component and a finger cover for makingcontact with an object (U.S. patent application Ser. No. 09/610,968).This force sensor detects dynamic variation in contact force when thewearer manipulates an object. However, it is not able to measurethree-dimensional motion of the fingers when an object is manipulated.

[0019] An object of the present invention is therefore to provide anapparatus for acquiring human finger manipulation data that, byaccurately measuring not only fingertip contact force during grasping ofan object with the fingertips but also three-dimensional motion of thefingers grasping the object, enables analysis of manipulative motions ofthe human hand.

SUMMARY OF THE INVENTION

[0020] To achieve this object, the present invention provides anapparatus for acquiring human finger manipulation data comprising atleast one finger motion detector composed essentially of a force sensorcapable of being fitted on a human fingertip, at least three links andat least four angle detectors; and a base supporting the finger motiondetector, wherein the base is attachable to an external mount or a humanhand, the force sensor is fittable on a human finger and connected tothe base through a link mechanism constituted by the plurality of links,the at least four angle detectors are attached at pivots between thelinks constituting the link mechanism and optionally at a pivot betweenthe link mechanism and the base, three-dimensional motion of the fingeris determined by measuring data of the angle detectors of the linkmechanism, and fingertip contact force is measured by the force sensor.

[0021] The angle detectors can be potentiometers, encoders or the like.

[0022] Not fewer than one and not more than five finger motion detectorscan be supported on the base.

[0023] An inclination angle sensor can be installed on the base formeasuring inclination of the base relative to vertical.

[0024] The base can be attached to a glove to be worn on a human hand.

[0025] The apparatus for acquiring human finger manipulation dataaccording to the invention thus enables acquisition of data not onlyregarding contact forces acting on human fingertips but also regardingthree-dimensional motion of the fingers at the time of grasping anobject. By using the acquired data to analyze the manipulative actionsof the human hand it becomes possible to develop a robot hand graspingand manipulation algorithm that takes advantage of human knowledge andexperience, and by this to enable a robot hand to grasp and manipulatepaper, cloth, cable and other flexible materials.

[0026] The above and other objects and features of the present inventionwill become apparent from the accompanying drawings and followingdetailed description.

BRIEF EXPLANATION OF THE DRAWINGS

[0027]FIG. 1 is an explanatory view showing the basic configuration ofan apparatus for acquiring human finger manipulation data according to afirst embodiment of the present invention.

[0028]FIG. 2(a) is a cross-sectional view showing an example of asix-axis force sensor, designed to fit on an operator's finger, used inthe data acquisition apparatus of FIG. 1.

[0029]FIG. 2(b) is a cross-section taken along line II-II in FIG. 2(a).

[0030]FIG. 3 is a perspective view of an example of an elastic componentused in the force sensor of FIG. 2.

[0031]FIG. 4 is an explanatory view of an apparatus for acquiring humanfinger manipulation data that is a second embodiment of the presentinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0032]FIG. 1 is an explanatory view showing the basic configuration of agrasp data acquisition apparatus for the human hand according to thepresent invention. The apparatus comprises a finger motion detector 9including a force sensor 1 to be worn on a human finger, at least threelinks 2 and at least four angle detectors 3, and a base 5.

[0033] The finger motion detector 9 is supported by the base 5. In theembodiment illustrated in FIG. 1, the base 5 is fastened to an externalmount 5′. Alternatively, it can be mounted on the hand of the operatoras shown in the embodiment of FIG. 4 explained later. The links 2 areinterconnected by pivots 4 to be rotatable relative to one another,thereby constituting a link mechanism. The distal link 2 of the linkmechanism is connected to the force sensor 1 and the proximal link 2thereof is connected through a pivot to the base 5.

[0034] The angle detectors 3 are used to measure finger motion. One isprovided at the pivot 4 between each adjacent pair of links 2 and one atthe pivot 4 between the proximal link of the link mechanism and the base5. The angle detectors 3 can be conventional potentiometers, encoders orthe like.

[0035] FIGS. 2(a) and 2(b) show an example of the force sensor 1 used inthe apparatus for acquiring human finger manipulation data of thepresent invention. As shown, the force sensor 1 includes a fingerstall20, an elastic component 21, a finger cover 22 and a link mounting lug23.

[0036] As shown in FIG. 3 by way of example, the elastic component 21 isstructured for ready distortion by specific force components. In theillustrated structure, the elastic component 21 is formed of a base 30and a ring 31 interconnected by three sectionally square beams 32. Eachbeam 32 has strain gauges 33 attached one to each of its four lateralsurfaces. When an external force is exerted on the elastic component 21,the beams 32 distort and the strain gauges 33 produce electric signalsin proportion to the distortion. The force components can therefore beread out in the form of electric signals.

[0037] A strain stiffness matrix expressing the relationship between thesix-axis forces (forces and moments in three orthogonal directions)acting on the elastic component 21 and the outputs of the strain gaugesof each beam is generated in advance by calibration and used to convertthe outputs of the strain gauges into force data. The six-axis forcesexerted on the elastic component 21 can therefore be calculated from theoutput signals of the strain gauges using the strain stiffness matrix.

[0038] The fingerstall 20 is for receiving the tip of the operator'sfinger. It is made of an elastic material such as engineering plastic,phosphor bronze, spring steel or the like and is formed with slits 25 tofacilitate insertion of different-sized fingertips. The fingerstall 20is connected to the base 30 of the elastic component 21.

[0039] As shown in FIGS. 2(a) and 2(b), the fingerstall 20 is alsoconnected to the distal link 2 of the link mechanism through the linkmounting lug 23. The finger cover 22, the member that makes contact withthe manipulated object, is connected to the ring 31 of the elasticcomponent 21 through a mounting block 24. The finger cover 22 is formedwith a cutout 26 so as to avoid contact with the link mounting lug 23.

[0040]FIG. 4 is an explanatory view of an apparatus for acquiring humanfinger manipulation data that is a second embodiment of the presentinvention. The finger motion detectors 9 a and 9 b shown in FIG. 4 aresubstantially identical to the finger motion detector 9 of FIGS. 1-3 inbasic structure but the common base 5 is fastened to a glove 8 worn on ahuman hand rather than to the external stationary member 5′.

[0041] The glove 8 is indicated by a broken line in FIG. 4, as iftransparent, so as to make it easier to understand the relationshipbetween the apparatus for acquiring human finger manipulation data andthe fingers. Although the illustrated embodiment has only the two fingermotion detectors 9 a and 9 b associated with the thumb and index finger,this is solely for easier explanation of the operating principle, andfinger motion detectors like that for the index finger designated byreference symbol 9 b can be incorporated in association with the otherfingers as required. The finger portions of the glove 8 are cut shortand the base 5 is fastened to the part at the back of the hand bysewing. An inclination angle sensor 6 is attached to the base 5.

[0042] After the operator has put on the glove 8 and inserted afingertip into each force sensor 1 (1 a, 1 b) of the apparatus accordingto this embodiment, monitoring of the contact force acting on thefingers and the motion of the fingers becomes possible. Explanation willbe made first with regard to the finger motion detector 9 a associatedwith the thumb. Three angle detectors 3 are installed at thecarpometacarpal (CM) joint (at the root of the thumb) and one at eachsucceeding joint to enable measurement of motions in three directions offreedom (opposition, adduction/abduction, flexion/extension) at the CMjoint, motions in one direction of freedom (flexion/extension) at themetacarpophalangeal (MP) joint (at middle of thumb), and motions in onedirection of freedom (flexion/extension) at the interphalangeal (IP)joint (at end of thumb).

[0043] More specifically, three angle detectors are provided in mutuallyorthogonal orientation in the vicinity of the thumb CM joint, from thebase 5 on through a link 2 e: an angle detector 3 e for detectingopposition motion of the CM joint, an angle detector 3 d for detectingadduction/abduction of the CM joint, and an angle detector 3 c fordetecting flexion/extension of the CM joint.

[0044] The angle detector 3 c at the thumb CM joint is connected througha link 2 c to an angle detector 3 b located above the thumb MP joint andthis angle detector 3 b is connected through a link 2 b to an angledetector 3 a in the vicinity of the thumb IP joint. A link 2 a extendingfrom the angle detector 3 a in the vicinity of the thumb IP joint isconnected to the link mounting lug 23 of a force sensor 1 a. The angledetectors 3 a, 3 b and 3 c measure thumb flexion/extension. Their axesof rotation are therefore oriented parallel to the axis of rotation ofthe thumb flexion/extension.

[0045] A finger motion detector 9 b is associated with the index finger(and optionally each of the middle, ring and little fingers). Two angledetectors 3 are installed at the metacarpophalangeal (MP) joint (at theroot of the finger) and one at each succeeding joint to enablemeasurement of motions in two directions of freedom(adduction/abduction, flexion/extension) at the MP joint, motions in onedirection of freedom (flexion/extension) at the proximal interphalangeal(PIP) joint (at middle of finger), and motions in one direction offreedom (flexion/extension) at the distal interphalangeal (DIP) joint.

[0046] More specifically, an angle detector 3 d for detectingadduction/abduction of the finger MP joint is attached to the base 5through a block 7. The axis of rotation of the angle detector 3 d liesperpendicular to the back of the hand, i.e., perpendicular to the uppersurface of the base 5. An angle detector 3 c for detectingflexion/extension of the finger MP joint is installed outward of theangle detector 3 d. The angle detector 3 c is connected through a link 2c to an angle detector 3 b located above the finger PIP joint and theangle detector 3 b is connected through a link 2 b to an angle detector3 a in the vicinity of the finger DIP joint.

[0047] A link 2 a extending from the angle detector 3 a in the vicinityof the finger DIP joint is connected to the link mounting lug 23 of aforce sensor 1 b. The angle detectors 3 a, 3 b and 3 c measure fingerflexion/extension. Their axes of rotation are therefore orientedparallel to the axis of rotation of the finger flexion/extension.

[0048] The operation of the apparatus for acquiring human fingermanipulation data will now be explained with reference to FIG. 4. Thehuman operator puts on the glove 8 and inserts the thumb and fingerswhose manipulative motions are to be measured into the fingerstalls 20of the force sensors 1 a and 1 b. After donning the apparatus in thismanner, the operator grasps/manipulates an object 11.

[0049] Specifically, the operator brings the finger covers 22 of theforce sensors 1 a and 1 b into contact with the object 11 and appliesforce to the grasped object 11 through the fingerstalls 20, elasticcomponents 21 and finger covers 22. The beams 32 of the elasticcomponent 21 located between the fingerstall 20 and the finger cover 22of each force sensor 1 are distorted in proportion to the amount offorce applied to the grasped object 11.

[0050] The strain gauges 33 of the force sensors 1 a and 1 b convert thedistortion into electric signals that are sent to a computer through anAID converter (neither shown). Using a strain stiffness matrix generatedbeforehand by calibration, the computer calculates the forces exerted onthe grasped object 11 from the outputs of the strain gauges 33.

[0051] The positions and the orientations of the fingertips arecalculated using the data from the angle detectors 3 a-3 e and knowndimensional parameters of the links 2 a-2 d. As a result, the motion ofeach fingertip can be calculated and plotted in an orthogonal coordinatesystem fixed to the base 5.

[0052] The data from the force sensors 1 a and 1 b is also plotted inthe coordinate system after coordinate-transformation using thefingertip position and orientation data. The inclination angle sensor 6is a conventional sensor for detecting inclination of the base 5relative to the direction of gravitational force (vertical). Theorientations of the fingertips relative to vertical are determined fromthe data obtained from the inclination angle sensor 6 and the angledetectors 3 a-3 e and used to compensate the force data from the forcesensors 1 a and 1 b for the force of gravity.

[0053] While the present invention has been described in the foregoingwith reference to specific embodiments of the apparatus for acquiringhuman finger manipulation data, it is not limited to the embodiments butcan be modified within the scope of the appended claims.

[0054] As explained in the foregoing, according to the presentinvention, an apparatus for acquiring human finger manipulation datathat is capable of measuring human finger motion and contact forceacting on the fingertips comprises at least one finger motion detectorconstituted of a six-axis sensor that can be easily worn on the humanfingertip, a link mechanism, and angle detectors.

[0055] The apparatus for acquiring human finger manipulation dataenables acquisition of human hand grasp/manipulation data usable foranalyzing the manipulative actions of the human hand and developing arobot hand grasping and manipulation algorithm that takes advantage ofhuman knowledge and experience, which in turn opens the way todevelopment of robot hands capable of grasping and manipulating paper,cloth, cable and other flexible materials that robots have heretoforefound difficult to handle.

What is claimed us:
 1. An apparatus for acquiring human fingermanipulation data comprising: at least one finger motion detectorcomposed essentially of a force sensor capable of being fitted on ahuman fingertip, at least three links and at least four angle detectors;and a base supporting the finger motion detector; wherein the base isattachable to an external mount or a human hand, the force sensor isfittable on a human finger and connected to the base through a linkmechanism constituted by the plurality of links, the at least four angledetectors are attached at pivots between the links constituting the linkmechanism and optionally at a pivot between the link mechanism and thebase, three-dimensional motion of the finger is determined by measuringdata of the angle detectors of the link mechanism, and fingertip contactforce is measured by the force sensor.
 2. An apparatus according toclaim 1 , wherein the angle detectors are potentiometers or encoders. 3.An apparatus according to claim 1 , wherein not fewer than one and notmore than five finger motion detectors are supported on the base.
 4. Anapparatus according to claim 2 , wherein not fewer than one and not morethan five finger motion detectors are supported on the base.
 5. Anapparatus according to claim 1 , further comprising an inclination anglesensor installed on the base for measuring inclination of the baserelative to vertical.
 6. An apparatus according to claim 2 , furthercomprising an inclination angle sensor installed on the base formeasuring inclination of the base relative to vertical.
 7. An apparatusaccording to claim 3 , further comprising an inclination angle sensorinstalled on the base for measuring inclination of the base relative tovertical.
 8. An apparatus according to claim 1 , wherein the base isattached to a glove to be worn on a human hand.
 9. An apparatusaccording to claim 2 , wherein the base is attached to a glove to beworn on a human hand.
 10. An apparatus according to claim 3 , whereinthe base is attached to a glove to be worn on a human hand.
 11. Anapparatus according to claim 4 , wherein the base is attached to a gloveto be worn on a human hand.
 12. An apparatus according to claim 5 ,wherein the base is attached to a glove to be worn on a human hand. 13.An apparatus according to claim 6 , wherein the base is attached to aglove to be worn on a human hand.
 14. An apparatus according to claim 7, wherein the base is attached to a glove to be worn on a human hand.